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  • 1
    Publication Date: 2022-10-26
    Description: Author Posting. © American Geophysical Union, 2019. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research: Biogeosciences 124(8), (2019): 2582-2594, doi: 10.1029/2019JG005107.
    Description: To assess the influences of carbon sources and transport processes on the 14C age of organic matter (OM) in continental margin sediments, we examined a suite of samples collected along a river‐shelf‐deep ocean transect in the East China Sea (ECS). Ramped pyrolysis‐oxidiation was conducted on suspended particulate matter in the Yangtze River and on surface sediments from the ECS shelf and northern Okinawa Trough. 14C ages were determined on OM decomposition products within different temperature windows. These measurements suggest that extensive amounts of pre‐old (i.e., millennial age) organic carbon (OC) are subject to degradation within and beyond the Yangtze River Delta, and this process is accompanied by an exchange of terrestrial and marine OM. These results, combined with fatty acid concentration data, suggest that both the nature and extent of OM preservation/degradation as well as the modes of transport influence the 14C ages of sedimentary OM. Additionally, we find that the age of (thermally) refractory OC increases during across‐shelf transport and that the age offset between the lowest and highest temperature OC decomposition fractions also increases along the shelf‐to‐trough transect. Amplified interfraction spread or 14C heterogeneity is the greatest in the Okinawa Trough. Aged sedimentary OM across the transect may be a consequence of several reasons including fossil OC input, selective degradation of younger OC, hydrodynamic sorting processes, and aging during lateral transport. Consequently, each of them should be considered in assessing the 14C results of sedimentary OM and its implications for the carbon cycle and interpretation of sedimentary records.
    Description: This study was supported by Doc. Mobility Fellowship (P1EZP2_159064; R. B.) from the Swiss National Science Foundation (SNSF). This study was also supported by SNF “CAPS‐LOCK” project 200021_140850 (T. I. E.), by the National Natural Science Foundation of China (NSFC; grants 41520104009 and 41630966, M. Z.), and by the “111” project (B13030). We are grateful for support of the NOSAMS staff in the execution of this project. We also appreciate the assistance from Yushuang Zhang (Ocean University of China) at NOSAMS and members of the Laboratory for Ion Beam Physics at ETH Zurich for AMS measurements. We acknowledge Lei Xing, Haidong Zhang, Guodong Song, Meng Yu, Yonghao Jia, and Shanshan Duan (Ocean University of China) for sampling assistance on the cruises. Assistance at sea by the crews of R/V Dongfanghong II and R/V Hakuhu Maru is also acknowledged. Readers can access or find the data from figures and tables in the supporting information.
    Keywords: Radiocarbon ; Carbon cycle ; Sediments ; Organic carbon ; Hydrodynamic processes
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 2
    Publication Date: 2022-10-26
    Description: Author Posting. © American Geophysical Union, 2021. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research: Oceans 126(1), (2021): e2020JC016802, https://doi.org/10.1029/2020JC016802.
    Description: The neodymium isotopic composition of the detrital (lithogenic) fraction (εNd‐detrital) of surface sediments and sinking particles was examined to constrain transport trajectories associated with hemipelagic sedimentation on the northwest Atlantic margin. The provenance of resuspended sediments and modes of lateral transport in the water column were of particular interest given the energetic hydrodynamic regime that sustains bottom and intermediate nepheloid layers over the margin. A large across‐margin gradient of ∼5 εNd units was observed for surface sediments, implying strong contrasts in sediment provenance, with εNd‐detrital values on the lower slope similar to those of “upstream regions” (Scotian margin) under the influence of the Deep Western Boundary Current (DWBC). Sinking particles collected at three depths at a site (total water depth, ∼3,000 m) on the New England margin within the core of the DWBC exhibited a similarly large range in εNd‐detrital values. The εNd‐detrital values of particles intercepted at intermediate water depths (1,000 and 2,000 m) were similar to each other but significantly higher than those at 3,000 m (∼50 m above the seafloor). These observations suggest that lithogenic material accumulating in the upper two traps was primarily advected in intermediate nepheloid layers emanating from the adjacent shelf, while that at 3,000 m is strongly influenced by sediment resuspension and along‐margin, southward lateral transport within the bottom nepheloid layer via entrainment in the DWBC. Our results highlight the importance of both along‐ and across‐margin sediment transport as vectors for lithogenic material and associated organic carbon transport.
    Description: This research was funded by the NSF Ocean Sciences Chemical Oceanography program (OCE‐0425677; OCE‐0851350). JH was partly supported by the National Research Foundation of Korea (NRF) grant funded by the Korean Government (2020R1A2C1008378).
    Description: 2021-06-04
    Keywords: Hemipelagic sedimentation ; Lateral particle transport ; Neodymium isotopes ; Nepheloid layers ; New England margin ; Sediment traps
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 3
    Publication Date: 2022-11-04
    Description: © The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Voss, B., Eglinton, T., Peucker-Ehrenbrink, B., Galy, V., Lang, S., McIntyre, C., Spencer, R., Bulygina, E., Wang, Z., & Guay, K. Isotopic evidence for sources of dissolved carbon and the role of organic matter respiration in the Fraser River basin, Canada. Biogeochemistry. (2022), https://doi.org/10.1007/s10533-022-00945-5.
    Description: Sources of dissolved and particulate carbon to the Fraser River system vary significantly in space and time. Tributaries in the northern interior of the basin consistently deliver higher concentrations of dissolved organic carbon (DOC) to the main stem than other tributaries. Based on samples collected near the Fraser River mouth throughout 2013, the radiocarbon age of DOC exported from the Fraser River does not change significantly across seasons despite a spike in DOC concentration during the freshet, suggesting modulation of heterogeneous upstream chemical and isotopic signals during transit through the river basin. Dissolved inorganic carbon (DIC) concentrations are highest in the Rocky Mountain headwater region where carbonate weathering is evident, but also in tributaries with high DOC concentrations, suggesting that DOC respiration may be responsible for a significant portion of DIC in this basin. Using an isotope and major ion mass balance approach to constrain the contributions of carbonate and silicate weathering and DOC respiration, we estimate that up to 33 ± 11% of DIC is derived from DOC respiration in some parts of the Fraser River basin. Overall, these results indicate close coupling between the cycling of DOC and DIC, and that carbon is actively processed and transformed during transport through the river network.
    Description: Open Access funding provided by the MIT Libraries. This work was supported by the WHOI Academic Programs Office, the MIT EAPS Department Student Assistance Fund, and the PAOC Houghton Fund to BMV; NSF-ETBC grants OCE-0851015 to BPE, VG, and TIE and OCE-0851101 to RGMS; NSF grant EAR-1226818 to BPE; NSF grant OCE-0928582 to TIE and VG; and a WHOI Arctic Research Initiative grant to ZAW.
    Keywords: River ; Carbon isotopes ; Radiocarbon ; Weathering ; Carbon cycle
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 4
    Publication Date: 2022-10-26
    Description: © The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Lattaud, J., Broder, L., Haghipour, N., Rickli, J., Giosan, L., & Eglinton, T., I. Influence of hydraulic connectivity on carbon burial efficiency in Mackenzie Delta lake sediments. Journal of Geophysical Research: Biogeosciences, 126(3), (2021): e2020JG006054, https://doi.org/10.1029/2020JG006054.
    Description: The Arctic is undergoing accelerated changes in response to ongoing modifications to the climate system, and there is a need for local to regional scale records of past climate variability in order to put these changes into context. The Mackenzie Delta region in northern Canada is populated by numerous small shallow lakes. They are classified as no-, low-, and high-closure (NC, LC, and HC, respectively) lakes, reflecting varying degrees of connection to the river main stem, and have different sedimentation characteristics. This study examines sedimentological (mineral surface area, grain size), carbon isotopic (bulk and molecular-level) and inorganic isotopic (neodymium) characteristics of sediment cores from three lakes representing each class. We find that HC lake sediments exhibit strikingly different properties from the other lake sediments. Specifically, they are characterized by higher organic carbon loadings per unit mineral surface area and with relatively minor influence from allochthonous, petrogenic (rock-derived) organic carbon. In contrast, LC and NC lakes have the potential to record basin-scale climatic changes at a high resolution by virtue of enhanced detrital sedimentation. Overall the delta lakes have the capacity to bury about 2 MtC year−1, with little changes in the last 200 years. However, in the (near) future, an increased number of high closure lakes might change the carbon burial efficiency of the Mackenzie Delta as they seem to retain less carbon than NC and LC lakes.
    Description: J. Lattaud was funded by a Rubicon grant (019.183EN.002) from NWO, Netherlands Organization for scientific research.
    Keywords: Bulk radiocarbon ; Carbon isotopes ; Mackenzie Delta ; Mineral loading ; N-alkanes
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 5
    Publication Date: 2022-10-26
    Description: © The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Schwestermann, T., Eglinton, T., I., Haghipour, N., McNichol, A. P., Ikehara, K., & Strasser, M. Event-dominated transport, provenance, and burial of organic carbon in the Japan Trench. Earth and Planetary Science Letters, 563, (2021): 116870, https://doi.org/10.1016/j.epsl.2021.116870.
    Description: The delivery of organic carbon (OC) to the ocean's deepest trenches in the hadal zone is poorly understood, but may be important for the carbon cycle, contain crucial information on sediment provenance and event-related transport processes, and provide age constraints on stratigraphic sequences in this terminal sink. In this study, we systematically characterize bulk organic matter (OM) and OC signatures (TOC/TN, C, 14C), as well as those from application of serial thermal oxidation (ramped pyrolysis/oxidation) of sediment cores recovered along an entire hadal trench encompassing high stratigraphic resolution records spanning nearly 2000 years of deposition. We analyze two cores from the southern and northern Japan Trench, where submarine canyon systems link shelf with trench. We compare results with previously published data from the central Japan Trench, where canyon systems are absent. Our analyses enable refined dating of the stratigraphic record and indicate that event deposits arise from remobilization of relatively surficial sediment coupled with deeper erosion along turbidity current pathways in the southern and central study site and from canyon flushing events in the northern study site. Furthermore, our findings indicate deposition of predominantly marine OC within hemipelagic background sediment as well as associated with event deposits along the entire trench axis. This implies that canyon systems flanking the Japan Trench do not serve as a short-circuit for injection of terrestrial OC to the hadal zone, and that tropical cyclones are not major agents for sediment and carbon transfer into this trench system. These findings further support previous Japan Trench studies interpreting that event deposits originate from the landward trench slope and are earthquake-triggered. The very low terrestrial OC input into the Japan Trench can be explained by the significant distance between trench and hinterland (〉180 km), and the physiography of the canyons that do not connect to coast and river systems. We suggest that detailed analyzes of long sedimentary records are essential to understand OC transfer, deposition and burial in hadal trenches.
    Description: The cruise was supported by the German Bundesministerium für Bildung und Forschung (BMBF 03G0251A) and the Deutsche Forschungsgemeinschaft. We acknowledge the Kochi core repository for additional surface samples of Japanese Cruises. Al Gagnon and Mary Lardie are thanked for their great help and technical assistance with the RPO instrument at NOSAMS. APM and the NOSAMS work were supported by the National Science Foundation Cooperative Agreement OCE-1239667. We appreciate the assistance from members of the Laboratory of Ion Beam Physics for the AMS measurements. Rui Bao is acknowledged for helpful discussions. A special thank you goes to Madalina Jaggi for her technical assistance for the C analysis of rinsed samples. This study was supported by the Austrian Science Fund (FWF P29678-N28) and a postgraduate grant by the International Association of Sedimentologists (IAS). We also acknowledge constructive support by the two reviewers (Jordon Hemingway and an anonymous). The authors declare no conflict of interests. The bathymetric data used in figure 1 is available at JAMSTEC-DARWIN database (http://www.godac.jamstec.go.jp/darwin/e) and Bundesamt für Seeschifffahrt und Hydrographie (https://www.bsh.de/DE/DATEN/Ozeanographisches_Datenzentrum/Vermessungsdaten/Nordpazifischer_Ozean/nordpazifik_node.html). Data of carbon analyses are displayed in the supporting information and also available from the corresponding author on reasonable request.
    Keywords: Carbon isotopes ; Carbon provenance ; Hadal zone event-stratigraphy ; Carbon transfer ; Japan Trench ; Ramped Pyr/Ox
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 6
    Publication Date: 2022-10-26
    Description: © The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Eglinton, T. I., Galy, V. V., Hemingway, J. D., Feng, X., Bao, H., Blattmann, T. M., Dickens, A. F., Gies, H., Giosan, L., Haghipour, N., Hou, P., Lupker, M., McIntyre, C. P., Montluçon, D. B., Peucker-Ehrenbrink, B., Ponton, C., Schefuß, E., Schwab, M. S., Voss, B. M., Wacker, L., Wu, Y., & Zhao, M. Climate control on terrestrial biospheric carbon turnover. Proceedings of the National Academy of Sciences of the United States of America, 118(8), (2021): e2011585118, htps://doi.org/ 10.1073/pnas.2011585118.
    Description: Terrestrial vegetation and soils hold three times more carbon than the atmosphere. Much debate concerns how anthropogenic activity will perturb these surface reservoirs, potentially exacerbating ongoing changes to the climate system. Uncertainties specifically persist in extrapolating point-source observations to ecosystem-scale budgets and fluxes, which require consideration of vertical and lateral processes on multiple temporal and spatial scales. To explore controls on organic carbon (OC) turnover at the river basin scale, we present radiocarbon (14C) ages on two groups of molecular tracers of plant-derived carbon—leaf-wax lipids and lignin phenols—from a globally distributed suite of rivers. We find significant negative relationships between the 14C age of these biomarkers and mean annual temperature and precipitation. Moreover, riverine biospheric-carbon ages scale proportionally with basin-wide soil carbon turnover times and soil 14C ages, implicating OC cycling within soils as a primary control on exported biomarker ages and revealing a broad distribution of soil OC reactivities. The ubiquitous occurrence of a long-lived soil OC pool suggests soil OC is globally vulnerable to perturbations by future temperature and precipitation increase. Scaling of riverine biospheric-carbon ages with soil OC turnover shows the former can constrain the sensitivity of carbon dynamics to environmental controls on broad spatial scales. Extracting this information from fluvially dominated sedimentary sequences may inform past variations in soil OC turnover in response to anthropogenic and/or climate perturbations. In turn, monitoring riverine OC composition may help detect future climate-change–induced perturbations of soil OC turnover and stocks.
    Description: This work was supported by grants from the US NSF (OCE-0928582 to T.I.E. and V.V.G.; OCE-0851015 to B.P.-E., T.I.E., and V.V.G.; and EAR-1226818 to B.P.-E.), Swiss National Science Foundation (200021_140850, 200020_163162, and 200020_184865 to T.I.E.), and National Natural Science Foundation of China (41520104009 to M.Z.).
    Keywords: Radiocarbon ; Plant biomarkers ; Carbon turnover times ; Fluvial carbon ; Carbon cycle
    Repository Name: Woods Hole Open Access Server
    Type: Article
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